1. FIELD OF THE INVENTION
This invention relates generally to nuclear reactors and in particular to circumferentially arrayed matching small gap displacements to limit component free end displacement of concentric components.
2. GENERAL BACKGROUND
The nuclear reactor in a nuclear power plant may often be subjected to excessive or unusual shock loadings resulting from seismic disturbances, earth tremors, or structural shocks caused by abrupt changes in temperature or fluid flow. During such times it is desirable to provide nuclear vessel components with seismic restraint at the free end opposite the supported end to prevent large dynamic loadings and resulting stresses in the component and/or vessel contents to prevent damage thereto. A variety of supports are utilized in previous structures.
U.S. Pat. No. 3,850,795 issued to Thome discloses an arrangement wherein a skirt is adjustably clamped and positioned through wedging means which bears against the reactor pressure vessel. Pads are joined to the inside surface of the pressure vessel and screw jacks fitted on the skirt within the pressure vessel engage the pads. The shapes of the pad bearing surfaces allow longitudinal displacement of the reactor structure.
U.S. Pat. No. 3,753,853 issued to Schabert discloses emergency supports between the nuclear container or core and the reactor pressure vessel. Vertical and removable radial support segments become effective only when a rupture of the pressure vessel occurs.
U.S. Pat. No. 3,771,499 issued to Maroni, Jr., et al. discloses a means for laterally supporting a nuclear steam generator against the effect of seismic loadings. Support is provided by means of a stiffening structure incorporating a shock suppressor apparatus which operates through the lever arm of a mechanical linkage.
U.S. Pat. No. 3,720,581 issued to Kaser discloses an inner shell and supporting structure for nuclear reactors of vertical inner shell plates which are not interconnected and horizontal section ribs extending between the plates and the wall of the reactor tank.
U.S. Pat. No. 4,008,757 issued to Weatherford, Jr. discloses a lubricated sliding structure for supporting massive heat exchangers. The lower surface of a forging on the bottom of the pressure vessel has a keyway slot. A support plate with a mating key is received within the slot and bolted to the bottom forging. The lower surface of the support plate has an arcuate surface that presses against a matching lubricating surface to transmit the entire vertical load to a concrete pedestal that has a means for cooling the concrete structure.
U.S. Pat. No. 3,554,868 issued to Thorp discloses a lower radial support system which permits free radial and axial differential expansion. A plurality of plates welded to the bottom of the reactor pressure vessel and a centering sleeve is fitted to the bottom support plate or a reactor core so as to have an interference fit on the inside diameter of the sleeve at operating temperature. The lower end of the sleeve is fitted to that plate structure with a tapered fit to permit vertical differential expansion of the reactor internals.
U.S. Pat. Nos. 3,123,328; 3,192,121; 3,563,855; 3,708,393; and 4,115,194 are representative of a variety of support structures in the art.
It is an object of the present invention to limit the vessel and core support horizontal displacements during a seismic occurrence.
It is another object of the present invention to reduce the accelerations and component dynamic ("G") loadings during a seismic occurrence.
In accordance with the above objects, it is a feature of the present invention to utilize small fixed gaps between local solid blocks.
It is another feature of the present invention to provide the reactor guard vessel and reactor vessel with thicker section roll-forged rings welded between the vessels straight shell sections and the bottom hemispherical head sections.